The CFE is the bootloader (like a PC BIOS/UEFI) for Broadcom devices. It's responsible for initial hardware configuration and subsequent booting of the (Linux OS) firmware. There are several variants of the WRT610N CFE. To find the CFE versions from within DD-WRT, run this from telnet/ssh, or use the Web GUI via "Administration->Commands->Run Commands":

For (most) Broadcom MIPS routers, DD-WRT has three branches: broadcom using the 2.4 kernel, broadcom_K26 (2.6 kernel), and broadcom_K3X (3.10 kernel). You can install the K2.4 builds on v1, but not v2. K2.6 supports both v1 and v2. To identify the difference, K2.4 builds aren't usually marked with any special identification, but K2.6 builds are in "broadcom_K26" folder with "K2.6" in the filename. K3.X is similar but supports v2 only.

For example, these are 2.4 kernel builds, only for v1 routers (THESE ARE NOT FOR INITIAL FLASH):

A simple way to recover a bricked device (confirmed to work with both CFE.12 and CFE.16) is:

unplug all ethernet ports (Important!)

unplug power

plug power in

wait 2-2.5 seconds

press the reset button and keep it pressed for 5 seconds, then release it

reconnect ethernet (DHCP shoud give IP address to computer)

point your browser at 192.168.1.1. You should see a "Management Firmware update" screen where you can flash the original firmware or dd-wrt directly (even mega builds).

Alternative Method 1:

manually assign 192.168.1.10 to your computer

unplug power

plug power in

wait 0.5-1.0 seconds

press the reset button and keep it pressed for 1 second, then release it

point your browser at 192.168.1.1.

Alternative Method 2:

manually assign 192.168.1.10 to your computer

unplug power

plug power in

wait for all lights blink

press the reset button and keep it pressed for 1 second or 3/4 flashes of the power-light, then release it

point your browser at 192.168.1.1.

The alternative methods are reported to work well on the wrt-610Nv1 CTGxxxx series (mostly works at the first attempt); these series are using CFE .16

On occasion, the recovery method will not accept a new dd-wrt image. Download the latest official WRT610N firmware from linksys and flash it back to the router via recovery method. Once the router is back online and you can navigate to the web gui, reflash dd-wrt to the router.

The management mode can also be activated from the serial console using

It seems that the WRT610n rev 1 and 2 have some issues when the wl1 (5ghz) interface is enabled, which have been experienced from r13064 to r14929 so far. When wl1 is enabled and WPA is activated, the router randomly disconnects its clients.

The apparent solution is to avoid any use of TKIP on the wl1 radio, and stick to AES encryption only (this does not work for everyone).

The on-chip switch currently doesn't properly support transitions from 100 Mbit/Gigabit to 10 Mbit; it will not renegotiate/fallback but stay in the previous mode, rendering the connection unusable. This is often a problem when Wake-On-Lan is to be used and the station to be woken switches to 10 MBit in standby mode for power preservation. Workaround for this case: some network interfaces allow setting the speed to be used for WoL idle mode, set this to 100 MBit.

As of build 12427, the router will randomly reboot, sometimes after minutes, sometimes after hours. Using only the 2.4 Ghz radio seems to make the problem occur less often. Developers are aware of the problem and are working on it.

A possible workaround seems to be disabling the interference mitigation mode using

wl -i eth0 interference 0
wl -i eth1 interference 0

either from telnet or from Administration->Commands.

See here (signature)
for real world uptimes of 3 different WRT610N devices, including their respective configurations.

Until build 12360, the 2.4 Ghz wireless radio MAC is always 00:90:4C:4E:00:2A. This causes weird client behavior if you have more than one WRT610N in one network. As a workaround, you can manually set the mac address using the shell commands

nvram set "pci/1/1/macaddr"=00:90:4C:D6:02:2a
nvram commit

This is fixed in 12427 for CFE.16 devices. For CFE.12 devices, the situation is now reversed: The 5 Ghz MAC always has 00:90:4C:4E:00:2A, and the 2.4 Ghz MAC is fine.

(not really an issue anymore)
Due to a problem in the CFE, it is not possible to recover a bricked device using the commonly recommended boot-wait TFTP process (i.e. by waiting for the device to react to pings to 192.168.1.1 and TFTP a firmware file to it). TFTP transfers to the device which are larger than 3.8MB (i.e., the stock firmware) will fail, other TFTP transfers will seemingly succeed, but the CFE will not flash them. See above for a much simpler way to unbrick using management mode. Debricking via serial port is also possible. Note that the serial port is externally accessible inside the "Internet" ethernet jack. Instructions for serial recovery are available here: http://www.dd-wrt.com/phpBB2/viewtopic.php?p=209668#209668

USB support works, including Hubs, for all kind of devices, even when Linksys only advertises this as a "Storage Link". Note that there are known Linux USB issues with USB 2.0, Hubs and Full/Low speed devices, notably the often used FTDI serial converters. Use USB 1.1 only as a workaround.

Not specific to the WRT610N, but with the 5 Ghz band, the channel limitations per regulatory domain are much broader than with 2.4 Ghz channels. Since dd-wrt doesn't limit the 5 Ghz channel selection, you run a much higher chance of setting the router to a channel which your client device (which does honor regulatory limits) doesn't support. See http://en.wikipedia.org/wiki/List_of_WLAN_channels#5.C2.A0Ghz_.28802.11a.2Fh.2Fj.2Fdraft-n.29 for a list of available 5 Ghz band channels.